Jet fuel composition



United States Patent Int. Cl. C10] N26 US. C]. 44-58 5 Claims ABSTRACT OF THE DISCLOSURE Jet fuel composition comprising a mixture of hydrocarbons boiling from 90 to 500 F. containing an effective anti-wear amount of a phosphate ester in which the ester groups have a total of from 6 to 10 carbon atoms.

This invention relates to a novel jet fuel composition exhibiting the unique property of reducing wear in a jet engine. The fuel of the invention is also outstanding in the case with which emulsions formed in the fuel due to the presence of water are removed. These important properties are obtained by incorporating in the fuel composition a minor amount of a phosphate ester compound represented by the formula: (RO) P=O in which each R represents an open chain aliphatic or aromatic radical and the total number of carbon atoms in said compound is from 6 to 10.

Either in aircraft usage or in stationary power installations, jet engines require the delivery of substantial volumes of fuel under pressure to the combustion zone of the engine. The fuel demands of the engine places a critical burden on the fuel pump which has the function of delivering the required fuel under the proper conditions. Jet fuel compositions, being light hydrocarbons, have little lubricity or lubricating value in themselves with the result that the fuel pump is operated under high wearinducing conditions. A lubricating oil cannot be employed in the fuel pump to alleviate this wear problem in order to avoid contaminating the fuel. The severe operating conditions referred to have caused serious breakdowns in jet fuel delivery systems due to excessive wear of the fuel pump mechanism.

Another critical problem encountered in the operation of jet engines and particularly in connection with the operation of jet engine aircraft is that caused by water in the fuel, the presence of a minor amount of which is inevitable. Water has a tendency to form emulsions with any additives present in the fuel and it is frequently the .case that these emulsions are not readily filterable from the fuel and are passed into the engine. Such emulsions can cause a blockage in the fuel feed system and actually bring the operation of the engine to a halt. The additive employed in the jet fuel of this invention is outstanding in that emulsions formed with the water contained in the fuel are readily separated as shown by the water separometer test.

The jet fuel of the invention comprises normally liquid hydrocarbons, that is light naphthas and kerosenes boiling in the range of 90 to 500 F., containing a phosphate ester compound or mixture of such compounds represented by the formula (RO) P=O in which each R represents an open chain aliphatic or aromatic radical and the total number of carbon atoms in the compound is from 6 to 10. More specifically, the jet fuel of the invention will contain from about 0.001 to 0.5 percent by weight of said phosphate ester. Preferred amounts of the anti-wear additive range from about 0.01 to 0.1 percent which correspond to about 27 and 270 lbs./ thousand barrels of fuel respectively.

Effective anti-wear phosphate ester additives of this 3,510,281 Patented May 5, 1970 invention include triethyl phosphate, triisopropyl phosphate, dimethyl phenyl phosphate, dimethyl xylyl phosphate and the like. In contrast to the foregoing effective additives, tricresyl phosphate, dimethyl cyclohexyl phosphate, tri-n-butyl phosphate, tri 2 ethylhexyl phosphate and trimethyl phosphate are ineffective as anti-wear additives in the fuel evidencing criticality in the group of effective phosphate esters.

The base fuel from which the jet fuel of the invention is prepared consists essentially of hydrocarbons boiling in the range from about to 500 F. Typical jet fuels which can be improved according to this invention include J P-3 a mixture of about 70 percent gasoline and 30 percent light distillate having a 90 percent evaporated point of 470 F., JP-4, a mixture of about 65 percent gasoline and 35 percent light distillate and JP-S, an especially fractionated kerosene having a high flash point and a low freezing point.

The following examples illustrate the practice of this invention. Base Jet Fuel A employed in these examples consisted of a 90 percent paraflinic-IO percent aromatic hydrocarbon mixture boiling in the range of 202 to 272 F. Base Fuel B consisted of a naphtha with distillation IBP of 330 F. and HP. of 501 F. Analysis and FIA The Four Ball Wear Test was employed to determine the improved anti-wear properties of the jet fuel composition of the invention. The test machine employed in this test comprises a system of four steel balls, three of which are in contact with each other in one plane in a fixed triangular position in a reservoir containing the sample and a fourth ball above and in contact with the other three. In carrying out the test, the upper ball is rotated while it is pressed against the lower three at any desired pressure by means of a suitable weight applied to a lever arm. The diameters of the scars on the three lower balls are measured by means of a low power microscope. The average diameter measured in two directions on each of the three lower balls is taken as a measure of the anti-wear characteristics of the fuel. Results of this test are given in Table I below:

TABLE I.WEAR TEST Four-ball wear test (5 kg. 600

r.p.m., 1 hr. RT)

Lbs/ bbls. scar, diameter,

Additive (PTB) mm.

Base fuel A, no edditive 0. 693 Trlethyl phosphate 90 0. 356 Trilsopropyl phosphate A. 90 0. 432 D methyl phenyl phosphate 90 0. 343 Dimethyl xylyl phosphate" 90 0. 356 Tri-n-butyl phosphate 90 0. 627 Tri-Z-ethylhexyl phospha 90 0. 673 Base Fuel B, no additive 0.572 Trieresyl phosphate 0. 572

The foregoing tests show the remarkable lmprovement having an output rating of 400 cc. per minute. The microammeter in the apparatus is set before water addition so that the Water Separometer Index value of the base fuel without Water is 100. Fuel and water are circulated for five minutes to insure complete mixing of the water-fuel mixture. A portion of this fuel mixture is then circulated through a glass system at a rate of 150 cc./min-. This efiluent passes through a glass fiber filter coalescer and then through a glass tube equipped with a light and photoelectric cell for determining the light transmission of the fuel from which the Water Separometer Index is determined. The Water Separometer Index value of the circulated fuelwater mixture is taken after the mixture has been passed through the glass filter. The higher the Water Separometer Index, the better the fuel is with respect to its water separation properties.

Base Fuel A described above after water addition had a Water Separometer Index value of 83. The same fuel containing both water and triethyl phosphate in a concentration of 90 lbs./ thousand barrels of fuel had a Water Separometer Index value of 100. This is a substantial improvement in the water separation properties of the additive-containing fuel and is of critical importance in the suitability of a jet engine fuel.

The novel jet fuel compositions of the invention have been shown to possess unusual anti-wear properties and excellent Water Separometer Index values. This improved fuel provides substantial advantages in maintaining both extended operation and reliability in the performance of jet engines.

Obviously, many modifications and variations of the invention, as hereinabove set forth, may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be made as are indicated in the appended claims.

I claim:

1. A fuel composition adapted for use in a turbine engine comprising a hydrocarbon mixture boiling in the range from about to 500 F. containing from 0.01 to 0.1 weight percent of a phosphate ester represented by the formula (RO) P O in which each R represents a radical selected from the group consisting of an open chain aliphatic and a phenyl radical, the total number of carbon atoms in said ester being from 6 to 10.

2. A fuel composition according to claim 1 containing from 0.01 to less than 0.1 Weight percent of said phosphate ester.

3. A jet fuel according to claim 1 in which said ester is triethyl phosphate.

4. A jet fuel according to claim 1 in which said ester is triisopropylphosphate.

5. A jet fuel according to claim 1 in which said ester is dimethyl phenyl phosphate.

References Cited UNITED STATES PATENTS 2,245,649 6/1941 Caprio. 2,261,290 11/1941 Rosen. 2,291,442 7/1942 Bass et al. 2,546,422 3/1951 Cross. 3,320,041 5/1967 He-mmingway 4458 DANIEL E. WYMAN, Primary Examiner Y. H. SMITH, Assistant Examiner U.S. C1. X.-R. 44--76 

